ENH: Wrote basic description in full documentation block.

Source/cmGlobalUnixMakefileGenerator.cxx

@@ -99,5 +99,8 @@ void cmGlobalUnixMakefileGenerator::GetDocumentation(cmDocumentationEntry& entry
 {
   entry.name = this->GetName();
   entry.brief = "Generates standard UNIX makefiles.";
-  entry.full = "full UNIX!";
+  entry.full =
+    "A hierarchy of UNIX makefiles is generated into the build tree.  Any "
+    "standard UNIX-style make program can build the project through the "
+    "default make target.  A \"make install\" target is also provided.";
 }